Boat keel



Aug. 1933- c. T. LUDINGTON 1,924,871

BOAT KEEL Filed June 26, 1931 3 Sheets-Sheet l 52; 5 6mm M26532? a /w H. W

A TTORNE Y.

Aug.

C. T. LUDINGTON BOAT KEEL Filed June 26, 1951 3 Sheets-Sheet 3 A TTORN E Y.

Aug, 29, T. LUDINGTON BOAT KEEL Filed June 26, 1951 3 Sheets-Sheet 3 III];

LII. 11

III

D I N V EJN TOR. 6/;67/51 E5 7. A (/0/A/6 TON A TTORNE Y.

Patented Aug. 29, 1933 UNITED STATES PATENT OFFICE Application June 26, 1931.

10 Claims.

This invention relates to boat keels and particularly to the fixed or adjustable keels of sail boats.

Sail boats as developed heretofore have been provided with areas of lateral resistance extending longitudinally of the boats and generically designated as keels, which may be fixed keels or vertically adjustable keels designated as centerboards. It is well known that the purpose of a keel is to prevent leeway when the vessel is working to windward. The leeway represents a lateral component of the force acting on the vessel. According to previous practice keels have been substantially rectangular in cross section and therefore provided with external substantially parallel plane faces which have been characterized by two disadvantages. They have reduced but not eliminated leeway, and they form such resistance as sharply to reduce the speed of the vessel or craft upon which they are mounted. The resistance is incident to the loss of energy occasioned by the formation of eddies as the planar surfaces move relatively to the water. The formation of eddies uses energy detracting from the longitudinal component of the force acting on the vessel. The inefiiciency as to leeway of the conventional keel is indicated by the established fact that the actual course of the vessel when heading up into the wind or beating to windward is angularly divergent from the theoretical course, delineated by the longitudinal axis of the craft, by an angle as wide as 5.

It is among the objects of this invention; to provide a vessel with a keel of high efficiency; to provide a vessel with a keel of lower resistance r and therefore to increase the speed of the vessel;

to provide a keel substantially precluding leeway; to provide a keel of such efficiency as to cause the vessel with which it is associated to work more or less to windward; to provide a keel of variable contour such as to secure a force component to windward of sufiicient power as to nullify the leeward component; to provide a keel of variable contour such as to be adjustable to its most efficient contour to give the most eificient performance according to the speed of the vessel with which it is associated; to provide an adjustable keel of airfoil contour by which is meant a keel of asymmetrical cross section such as to secure a desired windward lateral component through the relative motion of the keel and water; to provide an adjustable keel of selectively variable contour ranging from an asymmetrical airfoil section through a symmetrical streamline section to an opposite asymmetrical airfoil section; to provide a keel of asymmetrical contour whereby to develop Serial No. 546,947

a desired lateral component of force; and many other objects and advantages as will become more apparent as the description proceeds.

In carrying out the invention it is preferred to utilize a keel formed of two complementary portions arranged to form a symmetrical unit of streamlined contour or profile when operatively associated with each other, but each portion of asymmetrical airfoil contour so as individually to develop a lateral component selectively directed according to which of the two portions is used alone. Obviously the keel of this invention may be comprised solely of two relatively adjustable portions as of the centerboard or daggerboard type, or movable elements may be operatively associated with a fixed keel to selectively vary its profile or contour, or a permanently mounted deformable keel may be provided arranged for contour variation by suitable means within the keel to achieve the same result.

In the accompanying drawings:

Fig. 1 represents a side elevation of a diagrammatic sail boat with an adjustable keel according to this invention shown in section and in full lines with one centerboard'down and the other housed within the well,

Fig. 2 represents the-same as Fig. 1 except that the positions of the centerboard portions are reversed as to which is down and which is up,

Fig. 3 represents a horizontal section taken on line 33 of the lowered centerboard portion of Fig. 1, I

Fig. 4 represents a similar view taken on line 44 of Fig. 2,

Fig. 5 represents a fragmentary plan of a centerboard well as disclosed in Figs. 1 and 2 showing the streamline contour of the complementary portions of the centerboard unit, I

Fig. 6 represents a vertical section through the complementary halves of the centerboard unit according to one form of the invention,

Fig. 7 represents a similar vertical section through a slightly modified form of the centerboard unit,

Fig. 8 represents a diagrammatic side elevation of a sail boat with a centerboard'well shown in section and with the adjustable keel shown as of the daggerboard type,

Fig. 9 represents a horizontal section taken .on line 9-9 of the daggerboard of Fig. 8,

Fig. 10 represents a horizontal section of the complementary daggerboard of the pair of boards used with the form of invention shown in Fig. 8., no

Fig. 11 is a diagrammatic plan of a daggerboard well-plate with which is associated a fixed keel,

Fig. 12 represents a horizontal section through a form of daggerboard and fixed keel assembly as provided when both daggerboards are associated with the fixed keel of Fig. 11,

Fig. 13 represents a diagrammatic front elevation, partially in section, of a permanent deformable keel in which the contour of the keel is determined by the positioning of a movable skin on said keel, and as illustrated provides an arched or cambered surface on the starboard side of the keel,

Fig. 14 represents a diagrammatic horizontal section taken on line 14-14 of Fig. 13 illustrating the asymmetrical profile of such keel,

Fig. 15 represents a similar diagrammatic horizontal section through the keel shown in Fig. 13 with the cambered surface shown as on the opposite or port side of the keel from that disclosed in Figs. 13 and 14,

Fig. 16 represents a diagrammatic horizontal section through the keel of Fig. 13 with its normal symmetrical streamlined contour,

Fig. 17 represents a similar view with the flexible surface curved" outwardly on both sides of the keel to form a thicker streamlined keel section,

Fig. 18 represents a slightly enlarged fragmentary section through the deformable keel of Fig. 13 to show one mechanism for securing variable deformation of the keel, and

Fig. 19 represents a similar fragmentary section illustrating the sliding connection of the movable covering with the fixed portion of the keel of Fig. 13.

Referring to Figs. 1 and 2, the sail boat hull 10 has a centerboard well comprised of the fore wall 11, aft wall 12, port wall 13, and starboard wall 14, defining a well 15. The walls enumerated may delineate a rectangular well as has been customary in the past, or they may be so disposed as to conform to the contour of the centerboard unit to be described. For purposes of illustration the well has been disclosed as rectangular in cross section but provided with a contoured baffle strip 16 as shown in Fig. 5.

Mounted on the transverse pivot 1'? are a pair of complementary airfoil section centerboard elements 18 and 20. These may be designated respectively as the port and starboard centerboards. Considering the port centerboard element 18, it will be observed that in the section shown in Fig. 3 the profile is asymmetrical and is characterized by the substantially plane inner surface 21 and the cambered outer surface 22. The complementary starboard element 20 has the substantially plane inner surface 23 and the outer cambered surface 24. The arrangement is such that both boards may be lowered simultaneously to increase the area of lateral resistance, and this use of the cooperating elements presents a thickened centerboard of substantially streamline horizontal section as shown in Fig. 5. This section obviously may be indicated by placing the sections shown in Figs. 3 and 4 with their respective inner plane surfaces in substantial contact. It will be observed that the plane face 21 of board 18 is a chord line or chord of the asymmetrical airfoil profile 18. This chord is a straight line passing through. the entering and trailing edges of the airfoil section and obviously bears a predetermined angular relation to the longitudinal axis of the ship and is preferably either parallel to or coincident with the longitudinal vertical median plane of the ship. The plane face 23 of the opposite airfoil section 20 bears the same predetermined angular relation to the longitudinal axis of the ship (i. e. preferably parallel). When the centerboard sections are exposed together the meeting faces 21 and 23 form the chord of the symmetrical streamline whole, which chord also bears the same predetermined angular relation to the longitudinal axis of the ship. The normal use of such streamlined centerboard is in working before the wind. The double board need not be depressed very far in the water and has the definite advantage of preventing drift while practically eliminating eddy formation therefore owing to its reduced resistance securing the greatest possible speed from the sail boat.

In a beat to windward, however, with the wind on the port bow, for instance, centerboard element 20 is pulled up into the well leaving centerboard 18 as the exposed area of lateral resistance. Owing to the contour of element 18 there is provided an arched or cambered surface to windward and a substantially flat surface to leeward. While it is known that there will be certain pressures exerted on the plane surface 21, it is clear that the cambered or arched surface 22 develops a definite lateral appreciable component incident to the relative movement of the centerboard or adjustable keel 18 and the water. The production of such lateral component, through the smooth flow of the water on the arched surface will be readily understood by analogy with the principles of aerodynamics as exemplified, by the fiow of air by an airfoil. It has been discovered that the lateral component developed by the centerboard element is frequently of such intensity as not only to prevent leeway but positively or affirmatively to cause the boat to work further to windward so that the actual course traversed with relation to the wind may be even more acute than the angle between the longitudinal axis of the vessel and the wind. Conversely, and obviously, with the wind off the starboard bow centerboard element 18 may be retracted, and centerboard element 20 lowered to have a similar appreciable lateral component developed such as substantially to nullify the leeward component and thus to facilitate this heat to windward.

The profile of either of the centerboard elements 18 or 20 in vertical section is not of urgent importance except in so far as the contouring of the sections in substantially horizontal planes so as to be of airfoil section is facilitated. Thus there is disclosed in Fig. 6 a vertical section for the elements in which they each are tapered at the bottom. In Fig. 7 they are shown as substantially untapered.

Once the principle is known there are obviously many modifications which may occur to those skilled in the art. I illustrate in Figs. 8, 9 and 10 a daggerboard keel. In this form the boat 10 has the well 15 in which the port daggerboard 24 having the airfoil contour as shown in Fig. 9 similar to the section shown in Fig. 3 is vertically slidably disposed, and held against movement beyond a predetermined point by the flange 25 resting on top of the well 15. It will be understood that a complementary daggerboard 26 may be disposed in operative association with board 24 to form the streamlined Whole already described. Obviously either board may be removed and the other one permitted to remain in place according to the direction of the wind, with the same results as previously described. Obviously the chord of each asymmetrical airfoil section and of the symmetrical streamlined unit provided by both boards is of the same predetermined angular relation to the longitudinal axis of the ship.

While the dagger-boards 24 and 26 as illustrated in Fig. 8 may simply be placed back to back, it is contemplated that with larger boats it may be desirable to provide a fixed heel for the purpose of lowering the center of gravity of the whole by means of its own or an attached weight and with which one or the other of the daggerboards may be operatively associated to form the complete keel. Thus, as shown in Fig. 11, the daggerboard well may include a plate 19 having a fixed keel web 29 depending therefrom and which web includes substantially plane lateral faces 27 and 28 and a rounded edge 30 at its fore end and a rounded edge 31 at its aft end. Daggerboard openings 32 and 33 of daggerboard contour are provided adjacent web 29 of the keel so that selectively either daggerboard 24 or 26 may be pushed down through the opening 32 or 33 to sliding cooperating relation with the web 29.

With either board in position in its appropriate opening and in abutting engagement with the fiat surface of the keel web 29 it will be observed that the other flat keel surface will form the flat side of the assembled airfoil sectioned unit, the curved or arched surface of which will be comprised of the rounded edges 30 and 31 and the cambered surface of the associated daggerboard. As shown in Fig. 12 the assembly of fixed keel and both daggerboards in section forms a streamlined unit such as may be availed of when running before the wind. Obviously any devices to keep each board in contact with the keel web may be used as are found most expedient. Thus slots 8 may be provided on the boards arranged to slide upon streamlined buttons or lugs 9 on the web 29. In the case of the daggerboard and keel assembly of Figs. 11 and 12, it will be apparent that a straight line extending through the middle of the curved entering edge 30 and the tapered trailing edge 31 of the fixed web 29 comprises the chord of predetermined angular relation to the longitudinal axis for all of the forms of keel provided by assembly and disassembly of the respective daggerboards 24 and 26.

It is contemplated that a fixed keel may be provided which may have a fiexible covering or be otherwise disposed so as to be selectively deformable to arch one side or the other or both and to various degrees by mechanical or other means to secure the desired profile of the resistance area. This phase of the invention is embodied in the purely illustrative form of the disclosure of Figs. 13 to 19 inclusive. The boat hull 34 has the permanent keel 35 depending from the center thereof and may be constructed or built in any manner so as to provide a permanent stationary inner reinforcing device. The keel 35 may join the hull 34 at right angles by means of the provision of a fiat under surface 36 with relation to which the covering skin of the invention may have sliding movement. The bottom of the permanent keel 35 may have the streamlined weight or enlargement 37 having the plane upper surface 38 parallel with the bottom surface 36 of the hull and also provided to permit sliding movement of the flexible covering to be described. The entering edge of the keel 40 forms the point of attachment of a resilient sheet metal skin 41 extending from the entering edge 40 toward the trailing edge 42, on one side by the section 43, and on the other by the section 44. The skin 41 may if desired be comprised of one piece of material or of multiple pieces according to conditions. The rearward edges of sections 43 and 44 are anchored to the trailing edge of the keel 35 in such a manner as to permit fore and aft sliding of the rear edges or" the sections. This attachment may be accomplished in any desired manner such as by the provision'of flanged lugs or ears 45 on the inner faces of the respective sections engaging in undercut slots 46 formed in the permanent keel 35.

Any desired means may be used to secure proper positioning of the respective sections relative to the permanent keel 35 and the means disclosed is to be considered as purely illustrative and as obviously susceptible to many modifications. A control shaft 4"! having an operating device such as a crank 48 within the boat, extends vertically through the stationary keel-35 and may be provided with a series of arms 50 rigidly engaged by the shaft 47 and disposed in longitudinally extending lateral slots 51 formed in the keel 35. Each arm 50 is pivotally connected with a link 52 pivotally connected to the inner surface of the section 43. Any desired means, such as a friction clutch, a dog, a pawl, or the like 53 may be provided to hold the control shaft 47 in a desired position of adjustment. A control shaft 54 having an operating arm or lever 55 is mounted rotatably in keel 35 and has similar operative connection with the section 44.

It will be understood that with control shafts 4'7 and 54 properly adjusted both sections 43 and 44 will be held inwardly against the outer sides of keel 35 and'that the outer surfaces of sections '43 and 44 conform substantially to the contour of keel 35. Although the particular profile of the permanent keel 35 of itself is relatively unimportant, as the lateral faces thereof may lie in parallel planes or may be streamlined so that the lateral faces converge toward the trailing edge, it is preferred that the keel 35 have substantially the profile illustrated in which each face is of a modified flattened ogee curve, as more efiicient results are derived from the keel when the so called "flat portion of the airfoil section has such curvature on the opposite side to the highly arched or cambered surface by the outwardly flexed section. It will be understood that a straight line passing through the entering edge 40 and the trailing edge 42 willcomprise a chord of all of the symmetrical and asymmetrical contours derivable from the keel illustrated and that this chord obviously has a fixed predetermined angular relation to the longitudinal axis or the ship.

It is of importance in connection with the modification last described that the flexible or resilient skin be susceptible to an infinite range of deformation in order to obtain the profile best suited for conditions existing at the moment of adjustment. It being understood in this regard that it is preferable to have a high camber or arch when the boat is moving slowly, but to have a low camber or arch at higher speeds. The deformable permanent keel permits such graduated settings as to secure high efficiency under all operating conditions.

The form of the invention last described being diagrammatic indisclosure, obviously will be so constructed as regards strength and certainty of operation as will occur to those skilled in the art, and such modifications are to be construed as within the scope of this invention. It is of importance in this invention that the chord of alternate forms of airfoil profile of keel be angularly fixed in order that the eificiency of the invention may be attained. In other words, it is important that the change of keel contour from a camber on one side to a camber on the other side be accomplished without variation in the angular relation of the chord of the respective airfoil sections so that the lateral component derived from either airfoil profile is not accompanied by a rearward or drag component such as might be incident to a change of angular relation of the chord. In the preferred form, and as illustrated, the chord of all of the forms of symmetrical and asymmetrical profiles are at substantially zero angle relative to the longitudinal axis of the ship.

I claim:

1. In boats, at keel, said keel including a pair of complementary vertically relatively adjustable elements arranged to be disposed in lowered position together, each element of airfoil section asymmetrical relative to its chord horizontally of the element, the elements arranged to form a streamlined profile symmetrical with its chord in a predetermined relative position, the chord of said keel having the same predetermined angular relation to the longi udinal axis of the boat whether the profile be asymmetrical airfoil or symmetrical streamline.

2. In beats, a centerboard well, a pair of centerboard elements arranged to be projected together beneath the well, said elements forming a unit of substantially streamlined contour in horizontal section, said elements arranged for relative movement to expose a single element as 1 a resistance area, each element being of asymmetrical profile with an outer arched surface.

3. In boats, a center-board well, a pair of centerboard elements, means pivoting the elements relative to the well, the elements arranged for pivoting to project simultaneously beneath the contacting association to enable the elements to define a streamlined section when both together are exposed beneath the well.

4. In a boat having a longitudinal axis, an area of lateral resistance comprising an element one side of which is comprised of a substantially planar surface any horizontal line of which is substantially parallel with said axis, the other side of which element comprises a laterally arched surface, the respective surfaces of the element being joined at front and rear, the thicker part of the element being toward the entering edge thereof and said element arranged to develop an ap preciable lateral component in response to hydrodynamic reaction as the boat moves relatively to the water substantially longitudinally of said axis.

5. In boats, a centerboard keel having an initial streamlined horizontal contour with opposite surfaces substantially similarly cambered, means movable relative to the keel to vary the efiective horizontal contour thereof by increasing the camber of one lateral surface of the keel while still maintaining a streamlined contour to secure directionally predetermined lateral inoments through hydrodynamic reaction as the boat moves relatively to the water substantially longitudinally of the keel.

6. In boats, a centerboard normally of streamlined symmetrical horizontal profile with its thicker portion toward the entering edge thereof, and means for varying the horizontal profile of the keel of the centerboard to provide an asymmetrical airfoil horizontal profile the symmetrical and asymmetrical profiles being relative to a chord comprised of a straight line passing through the entering and trailing edges thereof of fixed angular relation to the boat.

7. In combination with a boat having a longitudinal axis, a centerboard initially of streamlined horizontal contour symetrical about a vertical plane containing said axis with its thicker portion toward the entering edge, means for selectively varying the horizontal contour of said centerboard from a fixed position of asymmetry relative to said plane with a cambered surface laterally on one side of said plane with its thicker portion toward the entering edge, to an opposite fixed position of asymmetry relative to said plane with a cambered surface on the opposite side of said plane with its thicker portion toward the entering edge.

8. In combination, aboat, a fixed centerboard on said boat of streamlined horizontal contour, a flexible skin on said centerboard, and means for adjusting the relative position of the skin and centerboard to provide variation in the effective horizontal contour of said centerboard.

9. In boats, a keel, said keel having a chord passing through the entering and trailing edges in predetermined fixed angular relation to the median vertical longitudinal plane of the boat, means for selectively varying the contour of the keel relative to said chord from symmetrical streamlined contour with its thicker portion toward the entering edge to asymmetrical airfoil contour with its thicker portion toward the entering edge, while maintaining said fixed angular disposition of said chord.

10. In boats, a keel, said keel having a chord comprising a straight line passing through the entering and trailing edges of the keel in predetermined fixed angular relation to the median vertical longitudinal plane of the boat, means for selectively varying the contour of the keel relative to said chord from asymmetrical airfoil contour with an arched surface on one side of said chord with its thicker portion toward the entering edge to asymmetrical airfoil contour with an arched surface on the other side of said chord with its thicker portion toward the enterdisposition of said chord.

CHARLES TOWNSEND LUDINGTON. 

